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Author Topic: Misfire when warm?  (Read 1803 times)

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colalowe

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Misfire when warm?
« on: 13 January 2007, 09:53:39 »
Hi all, My Omega has started to develop a misfire once its warm, from cold she drives fine.

She also had a full service at vauxhall about 6month ago and I had to change the plug leads due to a mis fire then but this sounds and feels different as it only seems to do it under load and once its warm!

Any Ideas?? :-[
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TheBoy

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Re: Misfire when warm?
« Reply #1 on: 13 January 2007, 10:04:16 »
Any EML coming on?

Any oil in plug wells?

Has DIS been changed?
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colalowe

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Re: Misfire when warm?
« Reply #2 on: 13 January 2007, 10:06:38 »
No there are no lights comming on and no oil, I havent changed the Dis yet as it runs fine when cold, it may be my next option though.

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Craig_R

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Re: Misfire when warm?
« Reply #3 on: 13 January 2007, 12:00:59 »
I Think The Boy is askng about the dissy pack as problems can start once the pack has gotten hot causing misfires

Craig
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TheBoy

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Re: Misfire when warm?
« Reply #4 on: 13 January 2007, 12:02:47 »
Missing under load with no EML frequently points towards HT issues. Given that leads have been changed, that leaves plugs and DIS. Or oil in plug wells....
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colalowe

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Re: Misfire when warm?
« Reply #5 on: 13 January 2007, 12:08:17 »
Thanks for the ideas,

 im going to check for oil in the plugs first, is there any way of checking an HT lead or is it a case of just having to buy a new set and see??
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colalowe

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Re: Misfire when warm?
« Reply #6 on: 13 January 2007, 12:10:53 »
I think ill just buy a DIS unit and replace that anyway as plugs and leads have been changed in the last 6 months, id be surprised if they have failed already.
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TheBoy

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Re: Misfire when warm?
« Reply #7 on: 13 January 2007, 12:18:22 »
The DIS is expensive (as are leads), so rule out other possibilities first.  The leads do not take kindly to hot oil, so leaking cam covers will ruin them. Oil in plug wells also will cause miss, and is again a sign of leaking cam covers.
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colalowe

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Re: Misfire when warm?
« Reply #8 on: 13 January 2007, 12:22:41 »
Cheers for that 'The Boy' I will definately check the wells for oil first as I know there is a slight leek from one of the cam covers so this may be the problem!
« Last Edit: 13 January 2007, 12:23:37 by colalowe »
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TheBoy

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Re: Misfire when warm?
« Reply #9 on: 13 January 2007, 12:31:26 »
Quote
Cheers for that 'The Boy' I will definately check the wells for oil first as I know there is a slight leek from one of the cam covers so this may be the problem!
Ahhh, change the cam cover gaskets (use genuine Vx, and BLACK sealant).

Empty the plug wells of oil (syringe, or kitchen roll) asap, as cats don't like misfires, and plugs/leads do not like being baked in oil...
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colalowe

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Re: Misfire when warm?
« Reply #10 on: 14 January 2007, 15:42:18 »
Today I had a look at the  plugs and sure enough plug No 3 was full of oil! Ive cleaned it out but the car still misfires, :(

How much will it cost to have the cam cover gaskets replaced and is it worth having the head gaskts replaced at the same time?? :-/
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TheBoy

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Re: Misfire when warm?
« Reply #11 on: 14 January 2007, 16:19:53 »
Quote
Today I had a look at the  plugs and sure enough plug No 3 was full of oil! Ive cleaned it out but the car still misfires, :(

How much will it cost to have the cam cover gaskets replaced and is it worth having the head gaskts replaced at the same time?? :-/
To change the gaskets, see the guide in Maintenece Guides section. And clean the breathers!
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Matchless

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Re: Misfire when warm?
« Reply #12 on: 14 January 2007, 21:45:39 »
You can check HT leads for broken connections using a multimeter on resistance. Measured resistance is proportional to length so its easy to spot one which is high resistance for its length or a broken one.
When the leads have been sat in oil the rubber seems to lose its insulating properties and the HT leaks to earth. Cant test for this except by substitution.

If it was a DIS pack breaking down then you would expect two cylinders to be misfiring, not one.
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Admin

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Re: Misfire when warm?
« Reply #13 on: 14 January 2007, 22:54:12 »
Quote
Today I had a look at the  plugs and sure enough plug No 3 was full of oil! Ive cleaned it out but the car still misfires, :(

How much will it cost to have the cam cover gaskets replaced and is it worth having the head gaskts replaced at the same time?? :-/

Cam cover gaskets are not too bad to replace. Probably about 3-4 hours the first time.
If taking to a garage ( :-/) make sure they know what 8nm is!! This is the torque setting of the cam covers. Tighten much more than this and you crush the gaskets causing leaks... again!

Also, as said before. The breather system MUST be cleaned thoroughly as the blockages in this cause the leakage.

As for changing head gaskets?  :o
Err, I really would not recommend it unless you feel you have far too much money and wish to dispose of a large sum of it for no good reason! ;)

Nothing wrong with the heads by the sound of it.

You may well need a replacement DIS pack though... (approx £80 off ebay, more from dealer!)
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colalowe

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Re: Misfire when warm?
« Reply #14 on: 20 January 2007, 20:32:23 »
Thanks to all the advice Ive had here so far,

the day after cleaning thoil out from the plug well she ran fine again and is still running fine now,
I get paid next week so first chance I get I will be changing the cam cover gaskets and cleaning the breather system, so fingers crossed that will sort the problem permenantly.

Cheers once again and Ill let you all know how I get on, (probably be back asking about how to get something of first no doubt!!) ;D

 :y
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Dave-C

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Re: Misfire when warm?
« Reply #15 on: 20 January 2007, 21:11:56 »
Yeah, "TheBoy" is dead right, use GENUINE gaskets and black goooooo. I fell for buying the cheapies, "Little mouthes to feed and all!" Two months later, had to do the same job again...  Kids now need a good feed, gotta wait until February for Weetabix, Now all OK. thanx to the advice from the Chappies & Lassies on here,

Dave C (Italian Red)
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devonian

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Re: Misfire when warm?
« Reply #16 on: 11 February 2007, 21:18:41 »
Hi guys, sorry to hijack this thread...

have now managed to get a 2.5cdx Omega, which seems to be suffering this problem. When on motorway, car warm ,trying to accelerate caused bad misires from engine and lack of power... :'(

previous owner had taken to garage local to him and they had diagnosed leaking cam covers as oil in spark plug sockets..they replace gaskets, spark plugs and HT leads...however problem still persists...have not had chance to check if cam cover still leaking...

Is this the same fault  :-/

Dave
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TheBoy

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Re: Misfire when warm?
« Reply #17 on: 11 February 2007, 21:21:24 »
Often, missing when warm with no EML is HT related...
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